But if your work consists of a lot of different cylinder heads the productivity of your seat and guide machine can be lost in set-up time. Our system has virtually no set-up time. Cutting the seat in three steps is actually one of the reasons our cutters are so accurate. If you are not completely satisfied with our tools, send them back for a full refund.
Actually this has been our policy for decades. It just seemed like the right time to remind you. The Neway Advantage For more than 50 years engine rebuilders of all shapes and sizes, from large production shops to backyard mechanics, have found the value of Neway valve seat cutters.
Find a cutter Valve Size 0. That is, if the blades of a 15 degree cutter will actually reach out to 38mm, the operating range for that cutter will state 36mm as the largest valve. In most cases you will find that there are two or three different cutter diameters that could work for a given valve size. You will narrow your choices down when you consider the angles that you need.
As you search through our cutters you will see that we offer both single-sided one angle only and double-sided two-angled cutters. Double-sided cutters offer the convenience of having two angles on one tool while single-angled cutters make it possible for you to purchase just the angle you need without having to pay for a second angle on the opposing side of the cutter cutter pricing is based on the quantity of carbide blades on the cutter.
Since you will need the ability to cut three angles you may wind up with three single-sided cutters, or one double-sided cutter and one single-sided cutter. It really makes no difference either way, the mission here is simply to cover our size range with the three angles we need. When there are multiple cutters to choose from, other considerations might help us boil it down. For example, we may have the option of choosing between five-bladed cutters and three-bladed cutters.
Five-bladed cutters cost more than three-bladed, as cutter pricing is based on the number of carbide blades on the cutter. For valve seat work requiring hefty stock removal, such as valve seat oversizing, five blades is definitely the way to go.
In terms of accuracy, there is no difference between the two. Neway offers three different series of valve seat cutters and pilots: standard series, small series, and heavy duty series. Standard series cutters work with standard series. Heavy duty series cutters and pilots. Remember, we prefer to use the valve head diameter as the reference point when we describe the operating range of our seat cutters. Your decision will be influenced first and foremost by the type of engine you are servicing.
If you're working on power equipment engines Briggs, Honda, Kohler, etc. If you're working on automotive engines, standard series is the way to go, with a few rare exceptions. At the time of this writing October, there are only about a half dozen automotive cylinder heads in the U. Before launching into the whys-hows-ifs, here's a short lesson in building a cutter kit. This is the most efficient way to build a kit. It is also possible, however, to select small series cutters at this same diameter nearly the same diameter that is.
This gap can be bridged by using the longer of the two blades TC blade that are used in the 1" cutters see Blade Swapping. When you have both series of cutters in your kit there will be, most likely, some sizes for which you will need both series of pilots for the same size; for example, a 5mm small series pilot and a 5mm standard series pilot. You will see this "duplication" in many of the motorcycle kits because there will be engines with very small seats and 5mm guides where small series cutters will be needed and other engines with 5mm guides where standard series cutter will be required.
The first thing to understand about the interference fit between a valve and valve seat is its purpose: to prevent reverse interference.
It's just that simple. If the valve face is a steeper angle than that of the valve seat you have reverse interference and this is not good. Reverse interference creates, obviously, the potential for combustion leakage. The second thing to understand about an interference angle is that even when it is not stated, there will always be some slight amount of interference engineered into the fit.
That is, even when the OEM calls for a "non-interference" fit i. When the valve is manufactured there will be a tolerance for the valve face angle and that tolerance might look like this: 45 degrees, plus zero, minus 30 minutes. For the seat angle the tolerance would run exactly the opposite: 45 degrees, plus 30 minutes, minus nothing.
You will, most likely, only find this level of detail on the drawings for the parts. It will not be stated in service manuals or tech bulletins. Of course when it comes to checking your work after reconditioning a valve seat, there will be a big difference in visual appearance between a non-interference fit and a one degree interference fit. With a full one degree interference angle only a thin line will appear on the valve face.
This line shows the contact at the outer edge of the 46 degree surface OD of seating surface , or the point where the 46 degree seating surface meets the flatter relief angle immediately adjacent to it, usually 31 degrees. It is important to understand that the seating surface will change "peen in" as soon as the engine fires so that the full width of the valve seating surface will contact the valve face. It is critical for the full width of the seating surface to contact the valve as the valve needs to transfer heat through this contact.
Some engine manufacturers still call for a full one degree interference angle 45 degree valve, 46 degree seat , but the trend has been toward a "non-interference" fit or rather, less interference in the fit , for some years now. The reason for this is that valve and valve seat materials are much more sophisticated these days and manufacturers are able to hold much tighter tolerances than before.
While we always defer to the OEM specification for a given application, in most cases there is no down side to cutting a 45 degree seat even though a 46 degree seating surface is called for, or vice versa. If you're going to stray from the OEM specification make sure to take the valve face angle into account.
For example, some Toyota engines call for a 45 degree seating surface with a 44 degree valve. In this case a 46 degree seat would not be such a great idea because would have 2 degrees of interference 44 degree valve, 46 degree seat.
Of course the blades are not adjustable or replaceable. The diameter listed for each respective cutter represents the outer diameter of the fixed carbide blades, so we use a slightly different approach in figuring out which cutter to use for a given application. Here's the "formula" for selecting the appropriate fixed blade cutter: take the valve head diameter and look for a cutter whose listed diameter the fixed blade OD is slightly bigger, anywhere from 1. We need the blade to extend out beyond the diameter of the valve head, but not so much bigger that it runs the risk of catching the chamber wall or some other obstruction.
A valve seat needs to be a band-like surface with a uniform width and sharply defined inner and outer diameters. The only way to create such a surface is to have relief angles above and below the actual seating surface, or contact surface. Yes, of course there is only one angle that the valve seals against, but it is the two relief angles above and below the seating surface that actually define that surface.
The narrowing angles give you the ability to control the width of the seating surface as well as the location of the seating surface on the valve face, another important component of a valve job.
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